Hourly and daily variations of surface ozone have been analyzed in relation to radon
and meteorological parameters to explore its controlling mechanisms. Measurements in
central Italy cover the years 2004 and 2005, showing a relevant role of transport in
the ozone concentration variability. An analysis based on back trajectories shows that the
site is affected by air masses originating from the west to northeast sector in about 74%
of the days, suggesting that L’Aquila could be considered a background site. The
background hypothesis is also supported by the rather low values of the following ozone
quantities: maximum of monthly averages (39 ppbv, July), annual median of hourly data
(29 ppbv), and annual average of hourly maxima recorded daily (49 ppbv). Only six
hourly data recorded ozone above 90 ppbv in 2 years but never above 100 ppbv. The
regression model reproduces measured ozone with accuracy in 67% of hourly
observations and 74% of daily mean data. Here the model includes information from the
following meteorological parameters: temperature, relative humidity, horizontal wind
speed/direction, sun radiation, and radon concentration. A tracer like radon that tracks the
dynamical changes of the lower atmosphere has a significant role in the model ozone
prediction improvement, especially for hourly observations and for the synoptic
component. In the first case (hourly observation), inclusion of radon data improves the
regression model performance by 5% (from 62 to 67%); in the last case (synoptic
component), the model accuracy increases by 3% (from 78 to 81%).

Hourly and daily variations of surface ozone have been analyzed in relation to radon
and meteorological parameters to explore its controlling mechanisms. Measurements in
central Italy cover the years 2004 and 2005, showing a relevant role of transport in
the ozone concentration variability. An analysis based on back trajectories shows that the
site is affected by air masses originating from the west to northeast sector in about 74%
of the days, suggesting that L’Aquila could be considered a background site. The
background hypothesis is also supported by the rather low values of the following ozone
quantities: maximum of monthly averages (39 ppbv, July), annual median of hourly data
(29 ppbv), and annual average of hourly maxima recorded daily (49 ppbv). Only six
hourly data recorded ozone above 90 ppbv in 2 years but never above 100 ppbv. The
regression model reproduces measured ozone with accuracy in 67% of hourly
observations and 74% of daily mean data. Here the model includes information from the
following meteorological parameters: temperature, relative humidity, horizontal wind
speed/direction, sun radiation, and radon concentration. A tracer like radon that tracks the
dynamical changes of the lower atmosphere has a significant role in the model ozone
prediction improvement, especially for hourly observations and for the synoptic
component. In the first case (hourly observation), inclusion of radon data improves the
regression model performance by 5% (from 62 to 67%); in the last case (synoptic
component), the model accuracy increases by 3% (from 78 to 81%).